openwrt/target/linux/ipq806x/patches/0026-pinctrl-msm-Silence-recursive-lockdep-warning.patch

From 9588c91936434166007c3a15ad7f4e2f3729c5e7 Mon Sep 17 00:00:00 2001
From: Stephen Boyd <[email protected]>
Date: Thu, 6 Mar 2014 22:44:40 -0800
Subject: [PATCH 026/182] pinctrl: msm: Silence recursive lockdep warning

If a driver calls enable_irq_wake() on a gpio turned interrupt
from the msm pinctrl driver we'll get a lockdep warning like so:

=============================================
[ INFO: possible recursive locking detected ]
3.14.0-rc3 #2 Not tainted
---------------------------------------------
modprobe/52 is trying to acquire lock:
 (&irq_desc_lock_class){-.....}, at: [<c026aea0>] __irq_get_desc_lock+0x48/0x88

but task is already holding lock:
 (&irq_desc_lock_class){-.....}, at: [<c026aea0>] __irq_get_desc_lock+0x48/0x88

other info that might help us debug this:
 Possible unsafe locking scenario:

       CPU0
       ----
  lock(&irq_desc_lock_class);
  lock(&irq_desc_lock_class);

 *** DEADLOCK ***

 May be due to missing lock nesting notation

4 locks held by modprobe/52:
 #0:  (&__lockdep_no_validate__){......}, at: [<c04f2864>] __driver_attach+0x48/0x98
 #1:  (&__lockdep_no_validate__){......}, at: [<c04f2874>] __driver_attach+0x58/0x98
 #2:  (&irq_desc_lock_class){-.....}, at: [<c026aea0>] __irq_get_desc_lock+0x48/0x88
 #3:  (&(&pctrl->lock)->rlock){......}, at: [<c04bb4b8>] msm_gpio_irq_set_wake+0x20/0xa8

Silence it by putting the gpios into their own lock class.

Signed-off-by: Stephen Boyd <[email protected]>
Acked-by: Bjorn Andersson <[email protected]>
Signed-off-by: Linus Walleij <[email protected]>
---
 drivers/pinctrl/pinctrl-msm.c |    7 +++++++
 1 file changed, 7 insertions(+)

--- a/drivers/pinctrl/pinctrl-msm.c
+++ b/drivers/pinctrl/pinctrl-msm.c
@@ -857,6 +857,12 @@ static void msm_gpio_irq_handler(unsigne
 	chained_irq_exit(chip, desc);
 }
 
+/*
+ * This lock class tells lockdep that GPIO irqs are in a different
+ * category than their parents, so it won't report false recursion.
+ */
+static struct lock_class_key gpio_lock_class;
+
 static int msm_gpio_init(struct msm_pinctrl *pctrl)
 {
 	struct gpio_chip *chip;
@@ -895,6 +901,7 @@ static int msm_gpio_init(struct msm_pinc
 
 	for (i = 0; i < chip->ngpio; i++) {
 		irq = irq_create_mapping(pctrl->domain, i);
+		irq_set_lockdep_class(irq, &gpio_lock_class);
 		irq_set_chip_and_handler(irq, &msm_gpio_irq_chip, handle_edge_irq);
 		irq_set_chip_data(irq, pctrl);
 	}